Car running lean

[Moose88x]

About 2 months ago I installed a PB5 oversized IM, The tuner 83mm TB, RS6 cast TBB, rs6 size bi pipes, and upgraded to Bosch 750cc injectors. I ended up going with Motoza for my tune. I have been having a hell of a time tracking down why I can’t get out of limp mode and getting lean codes and malfunction for both bank 1 and 2 o2 sensors. I have since replaced both o2 sensors and fixed a bit of broken down wiring from the harness, however still getting the codes for system too lean and malfunction in circuit for both B1 and B2. I have heard of the system is running SUPER lean this will flag both banks as malfunction but unsure if this is true.

PB5 sent me Sikky IM gaskets and I’ve used those and torqued to factory spec. Though the car is in limp mode after it has come up to temperature the car will pull hard, however when cold any acceleration causes a lean AFR. I have checked for boost leaks it holds up to 20PSI with no issues.

The car was previously tuned via GET Watkins stage 3 running methanol. The car ran fine with no issues with stock IM, TB, and 034 bi-pipes.

Any ideas? With the car running fine previously I am assuming that it may be the IM gaskets?
What are the chances it’s a cracked Exhaust Manifold? Or Exhaust Manifold gasket?


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[Silverex]

Doubt a leak around exhaust stuff will affect the AFR greatly without it being a very large obvious one.

I’m assuming you have a wideband O2 in car and been sending tuner logs?…what does he suggest?

[Moose88x]

Yup I’m running my wideband on one of the rear o2 sensors. They’re sending me a new ECU, MAP, and MAF. We’re going to try and pin point the exact culprit they believe that maybe my ECU could be bad. Very frustrating to say the least.


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[Moose88x]

My only reason I think it could be the EM or the EM gasket is that once the car is up to temperature during WOT (granted it only being soft limp mode 5PSI of boost the AFR is great but on cold start start up under WOT it goes lean. So I was assuming that the metal is heating up and expanding enough to seal whatever crack or gap there is.


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[Moose88x]

I’m unsure if anyone else has used SIKKY gaskets before, but they were sort of strange. They almost looked like a mini phenlonic spacer. They’re about 1/4” thick and made of a harder material, not completely solid. Thinking of maybe going back to OEM gaskets and see if that helps.


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[CELison]

Get a smoke tester. The 90 dollar Amazon ones work great. Paint can filled with mineral oil that you light on fire wire the battery. Add compressed air and boom…mekanic.